Can't find photos taken when I activate the camera with double tap on the back of iPhone 12 Pro Max. Where are they stored?

I enabled the shortcut to open the camera when double-tapping the back of my iPhone. It works, the camera opens and I can take a photo. What is annoying, is that it then displays the photo and asks me if I want to "Retake" it or "Use Photo"t. When I click on "Use Photo", I get a confirmation and the phone shows me again the locked screen. I have now two problems:

1) I can't find the photo afterwards in the Photo app. Have no clue where they are saved.

2) This doesn't work to take several photos, just one photo, which is very annoying.

If I take photos when the phone is locked by just pressing on the camera icon, the photos are taken normally and saved in the Photos app.

Why is going on with the camera and photos when double-tapping to take photos?

Thank you!